Technical Booklet D Structure·Page 49·4B.14
Flat roof joists - sizing and span tables
Tables 4B.35 to 4B.40 provide maximum clear spans for timber flat roof joists in strength classes C16 and C24, with different imposed load requirements depending on access type and roof slope.
Tables 4B.35 to 4B.38 give the maximum clear span of joists for a flat roof using timber strength class C16 and C24. The sizes, spacings and spans given will safely support the dead loads stated in the tables, together with a maximum imposed load of 0.75 kN/m2 or 1.00 kN/m2 or a concentrated load of 0.9 kN provided access is limited for the purpose of cleaning and maintenance only. Tables 4B.39 and 4B.40 are also given for a flat roof where the access is not limited to the purposes of cleaning and maintenance only and in these tables the imposed load is 1.5 kN/m2 or a concentrated point load of 1.8 kN.
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